Industrial Ethernet in the field of industrial applications
As we all know, in the enterprise information system, Ethernet has become the de facto standard network, industrial real-time control
System is an extension of traditional Ethernet to help users build a more open and integrated industrial automation and information network
The Industrial Ethernet technology, which is a combination of standard Ethernet and general industrial protocols. First he met the industry
Automated real-time requirements, the initial Ethernet using CSMA / CD can not meet the real-time demand for industry, when
When the main use of the field bus and token ring network, with the technical improvements, the switch in real-time has been
(+ -100ns), distributed servo control, discrete control, process control to
Safety systems and all industrial applications, and support on-site and remote monitoring, diagnosis and configuration; of course,
EtherNet / IP products can also use other standard Ethernet services such as HTTP, SNMP, and so on. this means
, Industrial automation and enterprise information systems more direct integration, for example, no additional programming, the relevant personnel on
You can easily configure, diagnose, and monitor factory equipment through a web browser. In addition, EtherNet / IP also from
EMC, installation of all aspects of the provisions of the protection, to ensure that EtherNet / IP products, strict industrial environment adaptability.
Second, the characteristics of industrial Ethernet technology
2.1 communication certainty and real-time
Industrial control network is different from the ordinary data network is the biggest characteristic of it must meet the control role of real-time
The requirement that the signal transmission be fast enough to meet the certainty of the signal. Real-time control often requires some change
The amount of data is accurate and regularly refreshed. Because EtherNet uses CSMA / CD, the network load is large when the network
Transmission uncertainty can not meet the real-time requirements of industrial control, so the traditional Ethernet technology is difficult to meet the control
The system requires real-time requirements for accurate timing communications and has always been considered a "non-deterministic" network.
However, the rapid Ethernet and switching Ethernet technology development, to solve the Ethernet non-deterministic problem with
To a new opportunity to make this application possible. First, EtherNet's communication rate increased from 10M, 100M
Up to today's 1000M, 10G, in the case of the same data throughput, the increase in communication rate means that the network
The reduction of network load and the decrease of network transmission delay, that is, the probability of network collision is greatly reduced. Secondly, the use of stars
Type network topology, the switch will be divided into a number of network segments. The EtherNet switch has a number
According to the storage, forwarding function, so that the input and output data between the ports can be buffered, no longer made
Collision at the same time the switch can also transmit data on the network to filter, so that the number of nodes within each network segment
According to the transmission only in the local network segment, without having to go through the backbone, do not take up other network bandwidth
, Thus reducing the network load of all network segments and backbone networks. Again, full-duplex communication makes both ports two
Twisted pair (or two fibers) at the same time to receive and send message frame, it will not conflict. therefore
, The use of switched hubs and full-duplex communication, can make the conflict domain on the network no longer exist (full-duplex communication
), Or the probability of collision is greatly reduced (half-duplex), thus making EtherNet communication determinism and real-time greatly improved.
2.2 stability and reliability
Traditional EtherNet is not designed for industrial applications and does not take into account the adaptability of industrial site environments.
Want to. As the industrial site of the machinery, climate, dust and other conditions are very poor, so the industrial reliability of the device
Made a higher demand. In the factory environment, the industrial network must have better reliability and recoverable
Sexual and maintainability.
Industrial network security is another security issue that industrial Ethernet applications must consider. industry
Ethernet can be the traditional three-tier network system, that is, information management, process monitoring layer, field devices
Layer, synthesis, so that the data transfer rate faster, more real-time, and seamless integration with the Internet
, To achieve data sharing, improve the operational efficiency of the factory. But also introduced a series of network security to
, Industrial networks may be affected by viruses, hackers, illegal intrusion and illegal operations, such as network security
Threaten. Under normal circumstances, you can use a gateway or firewall on the industrial network and external network isolation,
But also through the authority of control, data encryption and other security mechanisms to strengthen the network security management.
2.4 bus power supply problem
Bus-powered (or bus-fed) means that the cable connected to the field device not only transmits the data signal, but also
Provide work power to field devices. For field equipment power supply can take the following methods:
(1) in the current Ethernet standards based on the appropriate modification of the physical layer of technical specifications, the Ethernet Manche
The signal is modulated to a DC or low-frequency AC power supply, and the two signals are separated from the field device.
(2) does not change the structure of the current physical layer, and through the cable in the idle cable to provide power for field devices.